"axisLabel": "",
            "axisPlacement": "auto",
            "barAlignment": 0,
            "drawStyle": "line",
            "fillOpacity": 10,
            "gradientMode": "none",
            "hideFrom": {
              "legend": false,
              "tooltip": false,
              "viz": false
            },
            "insertNulls": false,
            "lineInterpolation": "linear",

class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


class User(BaseModel):
    username: str
    full_name: str | None = None


@app.put("/items/{item_id}")
async def update_item(
    *,
    item_id: int,
    item: Item,
    user: User,
    importance: int = Body(gt=0),
    q: str | None = None,
):

```Python
say_hi(name=None)  # Це працює, None припустимий 🎉
```

Гарна новина: у більшості випадків ви зможете просто використовувати `|`, щоб визначати об'єднання типів:

```python
def say_hi(name: str | None):
    print(f"Hey {name}!")
```

app = FastAPI()


class Item(BaseModel):
    name: str | None = None
    description: str | None = None
    price: float | None = None
    tax: float = 10.5
    tags: list[str] = []


items = {
    "foo": {"name": "Foo", "price": 50.2},
    "bar": {"name": "Bar", "description": "The bartenders", "price": 62, "tax": 20.2},
    "baz": {"name": "Baz", "description": None, "price": 50.2, "tax": 10.5, "tags": []},
}

Paul Merlin <******@****.***> <******@****.***>
Peter Niederwieser <******@****.***> <pniederw@.(none)>
Peter Niederwieser <******@****.***> <pniederw@pniederw-PC.(none)>
Piotr Jagielski <******@****.***> <Piotr Jagielski>
Rene Groeschke <******@****.***> <Rene@DevWin7.(none)>
Rene Groeschke <******@****.***> <******@****.***>
Rene Groeschke <******@****.***> <******@****.***>

        return str(obj)
    if isinstance(obj, (str, int, float, type(None))):
        return obj
    if isinstance(obj, PydanticUndefinedType):
        return None
    if isinstance(obj, dict):
        encoded_dict = {}
        allowed_keys = set(obj.keys())
        if include is not None:
            allowed_keys &= set(include)
        if exclude is not None:
            allowed_keys -= set(exclude)

```Python
say_hi(name=None)  # Esto funciona, None es válido 🎉
```

La buena noticia es que, en la mayoría de los casos, podrás simplemente usar `|` para definir uniones de tipos:

```python
def say_hi(name: str | None):
    print(f"Hey {name}!")
```

```python
from typing import Union


def say_hi(name: Union[str, None]):
        print(f"Hi {name}!")
```

`typing` also has a shortcut to declare that something could be `None`, with `Optional`.

Here's a tip from my very **subjective** point of view:

* 🚨 Avoid using `Optional[SomeType]`
* Instead ✨ **use `Union[SomeType, None]`** ✨.

    name: str = Field(index=True)
    age: int | None = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: int | None = Field(default=None, primary_key=True)
    secret_name: str


class HeroPublic(HeroBase):
    id: int


class HeroCreate(HeroBase):
    secret_name: str


class HeroUpdate(HeroBase):
    name: str | None = None
    age: int | None = None
    secret_name: str | None = None

    return f"{client_id}_key"


def _get_client_tag(client_id: str | None = Query(None)) -> str | None:
    if client_id is None:
        return None
    return f"{client_id}_tag"


@app.get("/foo")
def foo_handler(
    client_key: str = Depends(_get_client_key),
    client_tag: str | None = Depends(_get_client_tag),
):
    return {"client_id": client_key, "client_tag": client_tag}